JP3239436B2 - Abnormality detection device for fuel evaporation prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting an abnormality such as leakage of fuel gas in a fuel evaporation apparatus for preventing evaporation of fuel gas generated in a fuel tank.

[0002]

2. Description of the Related Art Conventionally, in vehicles and the like, it is required to install a fuel evaporation prevention device in order to prevent a fuel gas generated in a fuel tank from being released into the atmosphere. The fuel evaporation prevention device adsorbs fuel gas as needed by an adsorber of a canister provided in a purge passage communicating the fuel tank with the intake pipe, and opens and closes a purge control valve according to an operation state of the internal combustion engine. In this device, the adsorbed fuel gas is appropriately introduced into an intake pipe and mixed into a fuel mixture to thereby prevent fuel evaporation.

In such a fuel evaporation prevention apparatus, a purge passage is usually formed by connecting a canister and an intake pipe with a rubber hose. If the rubber hose is bent and crushed, the fuel gas is not introduced into the intake pipe, but exceeds the fuel gas adsorption capacity of the adsorbent in the canister, and the fuel gas is released from the air holes. Further, the rubber hose may be damaged due to corrosion or the like due to contact with the alcohol component, and it is also conceivable that the rubber hose comes off due to a rise in pressure when the air hole of the canister is clogged with dust or the like. Also in this case, the fuel gas is released to the atmosphere.

Therefore, in order to detect the occurrence of such a situation, a pressure sensor is disposed in a purge passage between the canister and the intake pipe (hereinafter, referred to as an intake pipe side purge passage), and the detection result of the pressure sensor is normal. There has been proposed a device that determines that there is an abnormality in the fuel evaporation prevention device when the maximum pressure exceeds the maximum pressure at the time and when a predetermined pressure difference cannot be detected before and after switching the open / close state of the purge control valve (for example, Japanese Patent Application Laid-Open No. Hei 2
-130255). According to the apparatus described in this publication, it is possible to accurately detect the blockage of the air hole of the canister, the inability to open the purge control valve, and the breakage or dropout of the purge passage on the intake pipe side.

[0005]

However, in the fuel evaporation prevention apparatus, a rubber hose is used for a connecting portion of a purge passage (hereinafter, referred to as a tank-side purge passage) connecting a fuel tank and a canister. The fuel gas may be released to the atmosphere even if this side is damaged or dropped. On the other hand, in the conventional apparatus, even if the tank-side purge passage is damaged or dropped, it cannot be detected as abnormal.

According to the prior art, if a pressure sensor is provided also in this tank side purge passage, it seems that breakage and dropout there can be detected in the same manner. However, there is the following problem. I didn't go.

The pressure of the fuel gas from the fuel tank is constantly applied to the tank-side purge passage. For this reason, the detection value of the pressure sensor attached here is greatly affected by the evaporation amount of the fuel gas in the fuel tank. The fuel gas evaporation amount of the fuel tank is not constant, but changes depending on the remaining fuel amount, the outside air temperature, the fuel consumption state, and the like. Therefore, simply adding a pressure sensor to the tank-side purge passage cannot detect damage or the like of the tank-side purge passage due to the amount of evaporation of the fuel gas.

Further, in the conventional apparatus, since the pressure sensor is attached to the intake pipe side purge passage, the structure must be able to withstand a wide range of pressure change from the negative pressure of the intake pipe to the atmospheric pressure. Therefore, the pressure detection sensitivity is low, and accordingly, the abnormality detection accuracy is low.

Therefore, in the present invention, as a first object, when there is an abnormality such as breakage anywhere in the entire fuel evaporation prevention device from the fuel tank to the intake pipe, this can be reliably detected. A basic configuration of an abnormality detection device for a fuel evaporation prevention device is provided.

In addition, as a second object, in particular, when there is an abnormality that causes a leak such as breakage somewhere in the entire fuel evaporation system from the fuel tank to the intake pipe, it is necessary to reliably detect the abnormality. An abnormality detection device for a fuel evaporation prevention device that can be provided.

Further, as a third object, when there is a blockage abnormality such as a collapse of a hose somewhere in the whole fuel evaporation prevention device from the fuel tank to the intake pipe, not only the cause of the leak, but also this is surely solved. An abnormality detection device for a fuel evaporation prevention device which can be detected is provided.

In addition, a fourth object of the present invention is to provide an abnormality detection device for a fuel evaporation prevention device which can use a sensor having high pressure detection sensitivity and has high abnormality detection accuracy.

[0013]

SUMMARY OF THE INVENTION An abnormality detecting apparatus for a fuel evaporation prevention apparatus according to the present invention, which has been completed to achieve the first object, comprises a fuel tank and an intake pipe as illustrated in FIG. The adsorbent of the canister provided in the middle of the communicating purge passage adsorbs the fuel gas generated in the fuel tank at any time, and opens and closes a purge control valve according to the operation state of the internal combustion engine, thereby obtaining the adsorbed fuel. A fuel evaporation prevention device for appropriately introducing gas into an intake pipe to prevent fuel evaporation, pressure detection means for detecting a pressure state in the fuel evaporation prevention device, and fuel evaporation prevention based on a detection result of the pressure detection means. An abnormality detection device for a fuel vaporization prevention device, comprising: an abnormality detection unit configured to detect an abnormality of an apparatus; an air hole closing unit configured to close an air hole provided in the canister; and the purge control valve. Sealing means for closing the entire fuel evaporation prevention device by closing both the air hole closing means and the air hole closing means, a closed section pressure adjusting means for adjusting the pressure of the sealed section to a predetermined pressure, and a closed section pressure adjusting means. Pressure change state measurement means for measuring a predetermined pressure change state at the time of pressure adjustment by means or after pressure adjustment, and the abnormality detection means detects an abnormality of the fuel evaporation prevention device from the pressure change state. It is characterized by the following.

In this basic configuration, for example, the closed section pressure adjusting means adjusts the pressure in the closed section by switching between a first predetermined pressure and a second predetermined pressure, and the pressure change state measuring means A first pressure change state after being adjusted to the first predetermined pressure, and a second pressure change state after being adjusted to the second predetermined pressure, respectively, and the abnormality detecting means includes: 3. The fuel evaporative protection device according to claim 2, wherein the first and second pressure change states are compared to detect an abnormality of the fuel evaporative emission prevention device. It can be developed into an abnormality detection device.

According to the second aspect of the present invention, the section from the fuel tank to the intake pipe is formed as one closed section by providing the air hole closing means and the sealing means. be able to. If there is a leak cause in any of these sealed sections due to breakage, falling off of the rubber hose, etc., gas leaks from the sealed section to the atmosphere or vice versa based on the difference between the internal pressure of the sealed section and atmospheric pressure. . The gas leak rate changes with the pressure difference. If the cause of the leak exists, the difference between the relative pressure difference from the atmospheric pressure between the case where the pressure is adjusted to the first predetermined pressure and the case where the pressure is adjusted to the second predetermined pressure by the closed section pressure adjusting means. , The leak rate changes. Therefore, if a predetermined difference is found between the first and second pressure change states measured by the pressure change state measuring means, a leak cause exists somewhere in the closed section, and such a difference is detected. Otherwise, there is no leak cause. "

Further, in order to achieve the third object, in the abnormality detecting device for a fuel evaporation prevention device according to claim 1,
The closed section pressure adjusting means introduces a negative pressure from near the intake pipe end, the pressure change state measuring means measures a pressure change state at the time of introducing the negative pressure, and the abnormality detecting means The abnormality detection device for a fuel evaporation prevention device according to claim 3, wherein an abnormality of the fuel evaporation prevention device is detected based on a pressure change state at the time of negative pressure introduction.

According to the third aspect of the present invention, if there is a blockage in any part of the purge passage, the pressure detected by the pressure detecting means is scheduled when the negative pressure is introduced into the closed section from the intake pipe side. It takes a long time to reach a negative pressure state or does not reach such a negative pressure state. Therefore, it is possible to easily determine whether there is an abnormality related to the blockage by looking at the pressure change situation at the time of introducing the negative pressure.

According to a fourth aspect of the present invention, in the abnormality detection device for a fuel evaporation prevention device according to any one of the first to third aspects, the pressure detection means is provided in a section from the fuel tank to the canister. An abnormality detection device for a fuel evaporation prevention device, which is provided, has also been completed.

According to this configuration, the pressure detecting means can have a structure capable of withstanding a pressure fluctuation within the relief pressure range of the fuel tank, and the sensitivity can be increased accordingly. Therefore, even a very delicate pressure change state can be accurately detected, and the accuracy of abnormality determination can be improved.

As the pressure detecting means for realizing the present invention, for example, a semiconductor pressure sensor which detects pressure by utilizing a piezo effect accompanying deformation of a diaphragm can be used. This semiconductor type pressure sensor has a very thin diaphragm, and can detect pressure with high sensitivity. However, since water vapor is also generated in the fuel tank, water may adhere to the diaphragm. If moisture adheres, an error occurs such that the deformation of the diaphragm is not uniform. In addition, the diaphragm may be broken by freezing. In addition, gum or dust in gasoline may adhere to the diaphragm, causing an error in the amount of distortion, and it may not be possible to detect an accurate pressure.

Therefore, as a fifth object, in realizing each of the above-mentioned inventions, an abnormality detecting device for a fuel evaporation prevention device capable of always performing highly reliable abnormality detection without causing an error during use. We decided to provide.

In order to achieve the fifth object, a first aspect is provided.
5. The abnormality detection device for a fuel vaporization prevention device according to claim 4, wherein the pressure detection unit is configured to displace in accordance with pressure, a magnetic member attached to the displacement member, and a magnetic member attached to the displacement member. An abnormality detection device for a fuel evaporation prevention device, comprising a Hall element that changes output based on displacement, has also been completed.

As a result, pressure can be detected without any error even in a fuel tank in which moisture, gum or dust exists, and a highly reliable abnormality can be always detected.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 2 is a schematic configuration diagram of an abnormality detection device for a fuel evaporation prevention device according to an embodiment of the present invention. The air sucked in through the air cleaner 1 that filters the air is supplied to an intake pipe 2 connected to the air cleaner 1. A throttle valve 8 that opens and closes in conjunction with an accelerator pedal 6 is provided in the intake pipe 2. This intake pipe 2 is connected via an intake valve 10 to a combustion chamber 16 formed by a piston 12 and an internal combustion engine main body 14. Further, the combustion chamber 16 is connected to an exhaust pipe 20 via an exhaust valve 18.

On the other hand, a fuel tank 22 containing liquid fuel
Pump 24 for pressurizing / supplying fuel in the pump, and the intake pipe 2
Is connected to the fuel injection valve 26, and is configured to control the opening and closing of the fuel injection valve 26 to inject fuel. In addition, a communication pipe 28 connected to the fuel tank 22
Are connected to the canister 30. An adsorbent 34 for adsorbing fuel gas, for example, activated carbon is stored in the canister body 32. Thereby, the canister 30
Can adsorb the fuel gas generated in the fuel tank 22 through the communication pipe 28. Also, the canister body 3
At 2, an air hole 36 open to the atmosphere is formed so that air can be sucked into the inside. This air hole 36
Is provided with a canister closing valve 37 for closing this as required.

As shown in FIG. 3, when a predetermined voltage (for example, 6 V or more) is not applied to the coil 37a, the valve 37b is connected to the spring 37.
c to open the conduit 37d communicating with the air hole 36 of the canister body 32, and when a predetermined voltage is applied, the coil 37a is excited to move the valve body 37b against the urging force of the spring 37c. This is an electromagnetic on-off valve for closing the conduit 37d.

Further, one end of the supply pipe 38 is inserted into the hose connection portion 32a of the canister body 32, and
And the other end of the supply pipe 38 is connected to a purge control valve 40. One end of a supply pipe 42 is connected to the purge control valve 40, and the other end of the supply pipe 42 is connected to the intake pipe 2. The supply pipes 38 and 42 used here are formed entirely of a flexible material such as a rubber hose or a nylon hose. The communication pipe 28 connecting the fuel tank 22 and the canister 30 is also partially formed of a rubber hose or the like.

The fuel tank 22 is controlled by the supply pipes 38 and 42 and the communication pipe 28 attached to the purge control valve 40.
A purge passage from the intake pipe 2 to the intake pipe 2 is formed. The purge control valve 40 is interposed between the two supply pipes 38 and 42 for switching the intake pipe 2 and the canister 30 to be in communication or non-communication. 38 and 42 are configured to be connected and disconnected. The details are shown in FIG.

As shown, the purge control valve 40 includes a canister-side port 40a to which the supply pipe 38 is attached, an intake pipe-side port 40b to which the supply pipe 42 is attached, and a passage 40c between the ports 40a and 40b. A valve element 40d that opens and closes on the way, a spring 40e that urges the valve element 40d in the valve closing direction, and a coil 40f that performs a purge by moving the valve element 40d in the valve opening direction against the urging force of the spring 40e. And a solenoid on-off valve comprising: A voltage is applied to the coil 40f by a pulse signal. By continuously changing the ratio (duty ratio) of the pulse width to the cycle of the pulse signal, the ratio of the time in which the valve 40d is in the open position to the opening / closing cycle of the valve 40d is changed. The fuel gas purge flow rate can be controlled. FIG. 5 shows the relationship between the purge control valve drive duty and the purge flow rate.

The fuel tank 22 is provided with a pressure sensor 44. Also, the fuel tank 22 has -40 mm
A relief valve 22a for releasing the pressure when the internal pressure exceeds Hg to 150 mmHg is provided. Therefore, the section from the fuel tank 22 to the canister 30 is always kept below the pressure fluctuation within this relief pressure range. Therefore, it is sufficient to employ a pressure sensor having a structure capable of withstanding this relief pressure range.

The fuel injection valve 26, canister closing valve 37, purge control valve 40 and pressure sensor 44 are connected to an electronic control circuit 50, respectively. The electronic control circuit 50 includes a well-known CPU 52, a ROM 54 for storing control programs and data in advance, and a readable and writable RAM 5.
6 and an input / output circuit 58 are connected to each other via a common bus 60. The input / output circuit 58 is also connected to various operating state detecting means such as a throttle sensor 62, an idle switch 64, and a vehicle speed sensor 66. The CPU 52 controls the signals input from the operating state detecting means via the input / output circuit 58 and the ROM 54,
The fuel injection valve 26, the canister closing valve 37, the purge control valve 40
For example, a driving signal is output via the input / output circuit 58. In this way, the electronic control circuit 50 executes fuel injection control, canister purge control, abnormality detection control of the fuel evaporation prevention device, and the like.

Next, among the processes performed by the electronic control circuit 50, the abnormality detection control of the fuel evaporation prevention device will be described with reference to the flowcharts of FIGS. 6 and 7 and the timing chart of FIG.

When the key switch (not shown) is turned on, the abnormality detection control of the fuel evaporation prevention device is repeatedly executed at predetermined time intervals (for example, at every 256 msec) together with fuel injection control processing.

When the process is started, first, the vehicle speed sensor 6
Then, it is determined whether or not the vehicle speed SP = 0 based on the input signal from S6 (S100). When it is determined as "YES", it is determined whether or not the engine is idling based on the input signal from the idle switch 64 (S110). Note that S
If “NO” is determined in any of 100 and S110, the process is terminated as it is. That is, the abnormality detection is executed only when the vehicle is stopped and the vehicle is in the idling operation state. This is because the fuel tank internal pressure fluctuates during running on a rough road or turning, and it may not be possible to make a correct determination in the following steps. In addition, even when the vehicle is stopped, in the racing state, the engine speed is not stabilized, the internal pressure of the fuel tank becomes unstable, and there is a possibility that a correct determination cannot be made.

If the vehicle is stopped and the vehicle is idling, the process branches to various steps while determining to what stage the process has progressed at present (S120 to S140). There are four processes, the first to fourth stages.
To the third flag F1 to F3. When “0” is set to all the flags F1 to F3, that is, S120 to S140
Are all "NO", the first stage, and the routine goes to S150.

In the first stage, first, after completely closing the purge control valve 40, the canister closing valve 37 is fully closed to seal the section from the fuel tank 22 to the intake pipe 2 (S1).
50, S160).

That is, as shown in FIG. 8, the section from the fuel tank 22 to the purge control valve 40 is first adjusted to the same state as the atmospheric pressure through the atmosphere hole 36 by controlling the purge control valve 40 to be fully closed. Then, at a slightly later time, the canister closing valve 37 is fully closed to form a closed section adjusted to the atmospheric pressure (time T2).

Subsequently, the input signal from the pressure sensor 44 is immediately taken in, the tank internal pressure P1 'immediately after sealing is stored, and the timer T built in the electronic control circuit 50 is reset and started (S170). In the next step, S
It is determined whether 10 seconds have elapsed after the execution of step 170 (S180). Before 10 seconds, the first flag F1 is set to "1" (S190). This is the second stage. In the second stage, "YES" is determined in the step of S120, and "S100-
The process is repeated as “S120” → “S180” → “...”.
During this time, the detection value of the pressure sensor 44 rises from 0 mmHg according to the amount of fuel gas generated in the fuel tank 22, as between time T2 and time T3 in FIG.

Immediately after 10 seconds have elapsed, the input signal from the pressure sensor 44 is taken in, the tank internal pressure P1 "at this time is stored (S200), and 10 minutes after the sealing.
The amount of pressure change (hereinafter referred to as the amount of change under atmospheric pressure) ΔP1 during the second is calculated (S210), and the first flag F1 is reset (S220). Thus, the second stage is completed, and the process proceeds to the third stage.

In the third stage, first, the purge control valve 40 is switched from the fully closed state to the fully open state, and the timer T is reset and started (S230). When the purge control valve 40 is fully opened, the intake pipe negative pressure starts to be introduced into the closed section under the positive pressure as described above (time T3). Therefore, if there is no abnormality due to blockage in the purge passage portion, the detection value of the pressure sensor 44 starts to decrease.

In the next step, based on the input signal from the pressure sensor 44, the tank internal pressure PT becomes -20 mmH
It is determined whether the value has become equal to or less than g (S240). "N
O ”, 2 seconds after execution of the step of S230
It is determined whether or not c has elapsed (S250). 2 sec
Before the elapse, the second flag F2 is set to "1" (S26).
0). Thus, this time in step S120, "N
O "," YES "is determined in the steps of S130, and" S100-S130 "→" S25 ".
The process is repeated from "0" to "..." to enter a standby state. This standby state ends when S240 or S250 becomes “YES”. If "YES" is determined earlier in S250, the purge system, that is, the flag Fclose, which means that there is a blockage somewhere in the purge system from the fuel tank 22 to the intake pipe 2, is set to "1". Then, the abnormality notification lamp is turned on (S280).

On the other hand, if "YES" is determined first in S240, the second flag F2 is reset (S29).
0) Then, the purge control valve 40 is fully closed again (S30).
0), the input signal from the pressure sensor 44 is taken in, the tank internal pressure P2 'immediately after the closed section is set to the negative pressure closed state is stored, and the timer T built in the electronic control circuit 50 is reset and started (S310). The process has shifted from the third stage to the fourth stage.

As can be seen from the detection value of the pressure sensor 44 in FIG. 8, by executing the steps S290 to S310, the inside of the closed section is adjusted to a negative pressure of -20 mmHg. (Time T4). Therefore,
This time, the detection value of the pressure sensor 44 increases from −20 mmHg in accordance with the amount of fuel gas generated in the fuel tank 22 as between time T4 and time T5 in FIG.

In the next step, it is determined whether or not 10 seconds have passed after the execution of the step S310 (S32).
0). Before 10 seconds, the third flag F3 is set to "1" (S330). Thus, this time S120, S1
In step S30, “NO” is determined, and in step S140, “YES” is determined.
The process is repeated from “0 to S140” → “S330” → “...” To enter a standby state.

Immediately after the elapse of 10 seconds, the input signal from the pressure sensor 44 is taken in, the tank internal pressure P2 "at time T6 is stored (S340), and 1
The pressure change amount during the 0 sec (hereinafter referred to as the negative pressure change amount) ΔP2 is calculated (S350). Then, it is determined whether or not there is a leak based on the leak determination condition shown in Expression 1 (S360).

[0046]

## EQU1 ## If .DELTA.P2> .alpha..DELTA.P1 + .beta., "There is a leak." Α: Coefficient for correcting the difference in fuel evaporation due to the difference between atmospheric pressure and negative pressure. That is, if there is a leak cause in the sealed section from the fuel tank 22 to the purge control valve 40, the outflow from the closed section to the atmosphere occurs under the positive pressure, while the inflow from the atmosphere to the closed section occurs under the negative pressure. Occur. Therefore, “(negative pressure change amount △ P2) = (negative pressure change amount △ P2) = ((atmospheric pressure change amount △ P1) = (amount of evaporative gas generated in fuel tank 22) − (outflow amount from closed section to atmosphere)) (The amount of evaporative gas generated in the fuel tank 22) + (the amount of inflow from the atmosphere into the closed section) ”is larger. From this, the criterion 1 was derived.

If the determination condition of the formula 1 is satisfied, that is, if “YES” is determined in S360, a part causing a leak is located somewhere in the purge system from the fuel tank 22 to the intake pipe 2. The purge system leak flag Fleak, which means that there is, is set to “1” (S370), and the abnormality notification lamp is turned on (S280). On the other hand, when it is determined to be “NO”, the flags F1 to F3 are forcibly reset and the process ends (S380).

According to the present embodiment described above, in the fuel evaporation prevention device, the purge control valve 4
If a leak or blockage has occurred in the section up to zero, it can always be accurately detected regardless of the mounting position of the pressure sensor.

Further, by adopting a configuration for executing the abnormality detection processing while the vehicle is stopped and during idle operation, erroneous determination can be avoided. Further, the pressure sensor 44
It is only necessary that the structure be able to withstand the pressure within the operating range of the relief valve of the fuel tank 22, so that the structure does not have to withstand a large pressure fluctuation such as when it is mounted between the canister 30 and the intake pipe 2. Good. As a result, a highly sensitive sensor can be used, and the abnormality detection accuracy can be improved.

The modes of various abnormalities that can be detected in this embodiment are as follows. Case: Damage or dropout in the communication pipe 28 or the supply pipe 38 Under negative pressure, there is damage and inflow of air from the dropout part, but under positive pressure there is outflow to the atmosphere. , Can be notified of abnormalities.

Case: Bending, collapsing, etc. in the communication pipe 28 or the supply pipe 38 The pressure does not decrease even if a negative pressure is introduced, or it takes time for the pressure to decrease.
50 is "YES", and an abnormality can be notified.

Case: Unable to open purge control valve 40 Negative pressure cannot be introduced, and the same as in the case S2
"NO" at 40 and "YES" at S250, so that an abnormality can be notified. In the state where the adsorbent cannot be opened, the fuel gas adsorbed by the adsorbent in the canister cannot be introduced into the intake pipe 2, and thereafter the fuel gas adsorbing capacity of the adsorbent is exceeded, and the fuel gas is released from the air holes. Case: Drop of supply pipe 42 Negative pressure from intake pipe 2 could not be introduced, and "NO" in S240 and "Y" in S250, as in the case.
ES ", and an abnormality can be notified. It should be noted that the case is not a blockage but a drop-off, so the type of the abnormality is wrong. However, if the presence of the abnormality can be accurately determined, the object of the present invention can be achieved.

Case: Bending, crushing, etc. in the supply pipe 42 This is exactly the same as the case, and “NO” in S240 and “YES” in S250 based on the negative pressure introduction status.
And an abnormality can be notified. As in the case, there is a possibility that fuel gas may be released from the air holes, and this case is an abnormality that needs to be detected.

Case: Blockage of the Atmospheric Hole 36 of the Canister 30 This abnormality does not immediately cause a large pressure rise such as crushing or bending of the rubber hose. In the case where the supply pipes 38 and 42 are crushed or the like, the fuel gas cannot be purged even if the purge control valve 40 is opened, but the purge control valve 40 is opened even if the air hole 36 of the canister 30 is closed. This is because the fuel gas is sometimes purged accordingly. For this reason, the abnormality in which the air hole 36 of the canister 30 remains closed is not configured to be immediately found from the abnormality detection routine described above, but there is no major problem. If necessary, the tank internal pressure P is set in the process of S340 in the abnormality detection routine described above.
As soon as 2 "is detected, the canister closing valve 37 is opened, and if the pressure does not quickly return to the vicinity of the atmospheric pressure, it may be determined that the air hole 36 is abnormally closed.

Case: A state in which the purge control valve 40 cannot be closed. When this abnormality is present, the fuel gas is always introduced into the supply pipe 2. The fuel gas is not discharged from the atmospheric hole, and the fuel gas does not need to be abnormal from the viewpoint of preventing evaporation of the fuel gas. Therefore, in the above-described embodiment, a method for particularly detecting this abnormality is not provided. If necessary, S2
If ΔP1 calculated in step 10 becomes equal to or less than the predetermined negative pressure, it may be determined that the purge control valve 40 cannot be closed.

Case: A state where the supply pipe 42 is damaged such as a crack. Since the supply pipe 42 is a portion through which the fuel gas passes only when the purge control valve 40 is opened, even if there is a crack or a hole. This only functions in the same manner as the atmospheric holes 36 of the canister 30, and it is needless to say that there is no particular problem from the viewpoint of preventing fuel gas evaporation. Therefore, although this cannot be detected in the above embodiment, there is no problem.

It should be noted that cases 1 to 4 are common in that an abnormality can be determined based on a pressure change state after or after the pressure in the closed section is adjusted to a predetermined pressure.

Next, a second embodiment will be described. The second embodiment executes the same configuration and processing as the above-described embodiment, but is characterized in that a pressure sensor 100 of the type shown in FIG. 9 is employed.

The main body of the pressure sensor 100 is a cup 1
01 and the cap 103 are fitted. A pressure introducing pipe 10 opening into the fuel tank 22 is provided in the cup 101.
5 is provided, and one of the caps 103 is provided with a wire guide tube 107 for connecting a measuring wire. The inside of the cup 101 and the cap 103 are bisected by a diaphragm 109 fitted and fixed between the two.
In the space divided into two, a cup 101 and a cap 103
Stoppers 111, 11 protruding from respective inner walls of
3, the movement range of the diaphragm 109 is restricted.

The diaphragm 109 is made of fluoro rubber (FK).
M) having a thickness of 150 μ to 250 μ reinforced with a base cloth. Pressure receiving plates 115 and 117 are fixed to both surfaces of the diaphragm 109. And stopper 1
The pressure receiving plates 115 and 117 are in contact with the pressure receiving plates 11 and 113. Springs 119 and 121 are in contact with the pressure receiving plates 115 and 117 from above and below. Due to the balance between the springs 119 and 121 and the pressure introduced from the pressure introducing pipe 105, the diaphragm 109 is formed.
Is the fuel tank 22 between the stoppers 111 and 113.
At a position proportional to the internal pressure of the

The pressure receiving plate 115 on the electric wire guide tube 107 side
The rare earth magnet 123 is fixed at the center of the. A hybrid IC 127 including a Hall element 125 is provided at a position facing the rare earth magnet 123, and the displacement of the diaphragm 109, that is, the pressure in the fuel tank 22 is detected by the output of the Hall element 125.

In this pressure sensor 100, the fuel tank 2
When the pressure in 2 changes, the diaphragm 109 moves up and down in proportion thereto. Accordingly, the distance between the Hall element 125 and the rare earth magnet 123 changes, and the magnetic flux entering the Hall element 125 changes. As a result, from the Hall element 125,
A change in the output voltage corresponding to a change in the magnetic flux, that is, a change in the distance from the rare-earth magnet 123 occurs.

FIG. 10 shows the relationship between the Hall element output voltage and the magnet displacement. Although the Hall element 125 itself has a linearity of 2%, the Hall element output voltage and the magnet displacement are not linear as shown.
The output voltage of the Hall element 125 itself is about 100 mV, but the distance from the fuel tank 22 to the electronic control circuit 50 is considerable. Discrimination may not be possible.

For this reason, in the present embodiment, the amplifier circuit and the linear approximation circuit shown in FIG. 11 are incorporated in the hybrid IC 127. The amplification circuit is a Hall element 1
A temperature correction circuit 131 is connected to the battery input terminal 25 and an amplifier 133 is connected to the output of the Hall element 125. The linear approximation circuit includes a plurality of comparators 137 that receive an output signal of the amplifier 133 at one input terminal and receive reference voltages E1, E2,... At the other input terminal.
Each comparator 137 inputs a signal to the output unit 139. The terminal 141 of the output unit 139 and the electronic control circuit 50 are connected by a measuring wire, and the output voltage of the Hall element 125 is amplified and linearly approximated and input to the electronic control circuit 50.

As shown in FIG. 12, the pressure sensor 100 shares the battery line + B and the ground line GND with the fuel pump 24, and has a pump flange 225 mounted on an upper plate 221 of the fuel tank 22 via a gasket 223. It is fixed so that it penetrates. The fuel pump 24 is suspended via a pump bracket 231 so as to be located in a sub tank 229 fixed to a lower plate 227 of the fuel tank 22, and discharges fuel sucked from a fuel filter 233 from a discharge pipe 235. Things. Next to the discharge pipe 235 is a return pipe 237.

The fuel tank 22 of the pressure sensor 100
The mounting position to the camera is not limited to this, as shown in FIG.
Sender flange 2 to which fuel sender 255 of the type of remaining amount warning lamp 251 or float 253 is attached
57 and may be attached to the passage between the fuel tank 22 and the canister 30.

Although the pressure sensor 100 of this embodiment is mounted at a position where it is exposed to moisture, gum and the like from the fuel tank 22, the displacement amount of the rare earth magnet 123 as described above is measured by a hole. Since the configuration uses a rubber diaphragm having a thickness of 150 μm to 250 μm measured by the element 125, the operation of the diaphragm 109 due to the adhesion of moisture or the like is not significantly affected as compared with a semiconductor pressure sensor. Further, since it is not necessary to use an extremely thin diaphragm unlike a semiconductor type pressure sensor, there is no possibility of damage due to icing.

As a result, highly reliable pressure detection can be performed over a long period of time, and abnormality detection in the fuel evaporation prevention device can be accurately performed. In this embodiment, a rare earth magnet is used as the magnet, but it may be made of a ferrite magnet.

As described above, the present invention is not limited to such an embodiment, and can be implemented in various modes without departing from the gist of the present invention. For example, canister 3
The pressure sensor 44 may be attached to a section between the pressure sensor 0 and the intake pipe 2. Also in this case, it is possible to detect the presence or absence of a leak cause in the entire sealed section based on the pressure change state after forming the sealed section.

In adjusting the measurement start pressure after sealing, the negative pressure may be introduced by completely different means instead of opening and closing the purge control valve 40 to introduce the negative pressure. In addition, the change amount under atmospheric pressure ΔP1 and the change amount under negative pressure ΔP
Instead of comparing the pressure change with the pressure 2, the pressure change amounts ΔP1 and ΔP2 may be compared with each other as pressure changes from a positive pressure equal to or higher than the atmospheric pressure. May be. If the pressure value at the start of the measurement is different, the leak rate from the damaged part will be different.Therefore, the pressure adjustment condition of the closed section is set to the pressure equal to or higher than the atmospheric pressure or to the negative pressure. This is because the presence or absence of the cause of the leak in the closed section can be detected by paying attention to the difference.

Next, a third embodiment will be described. S3 in FIG.
At 60, regardless of the amount of fuel in the fuel tank 22,
Although the criterion for determining the leak was determined, as shown by the solid line in FIG. 14, even if the leak diameter in the closed section from the fuel tank 22 to the purge control valve 40 was constant, the fuel tank 22
The amount of change in the internal pressure of the fuel tank 22 greatly changes depending on the internal space volume, that is, the fuel amount. Therefore, the supply abnormality is detected based on the time when the space volume of the fuel tank 22 with the smallest pressure change is large (when the fuel amount is small).
In this case, when the space volume of the fuel tank 22 is small (when the fuel amount is large), an abnormal state is excessively detected even when the pressure changes when the leak diameter is small, which is not considered to be abnormal.

Therefore, the criterion for determining the leak is changed according to the fuel amount as shown by the broken line in FIG.
The leak diameter can be accurately determined. In order to perform such control, FIG. 15 shows the relationship between S350 and S360 in FIG.
Add step. That is, in S351, the fuel amount Fu in the fuel tank 22 is read based on the output of the fuel sensor 255, and in the next S352, the fuel tank 2 stored in advance in accordance with the read fuel amount Fu is read.
The correction coefficient γ corresponding to the space volume of No. 2 is obtained. And
In the next S360,

[0073]

If ΔP2> a · ΔP1 + β + γ, it is determined that “leakage has occurred”. Here, the correction coefficient γ is set to increase as the space volume decreases, so that the determination criterion changes as indicated by the broken line in FIG. 14 in response to the change in the space volume of the fuel tank 22. Of course.

Next, as a fourth embodiment, an abnormality detection control during running of the vehicle will be described. This embodiment corresponds to FIG.
5, the same configuration and processing as those of the third embodiment are executed. In particular, it is possible to detect an abnormality of the fuel tank internal pressure occurring during running on a rough road or turning by the fuel sender 255 to detect an abnormality. The feature is to determine whether or not.

An example of the determination that the fuel sender 255 can detect an abnormality will be described below. Fuel sender 255
Is input to the CPU, and the fuel sender 255 is provided at predetermined time intervals (for example, every 256 msec) from the start of abnormality detection or only during the calculation of ΔP1 or ΔP2.
It is determined whether or not the output is within a predetermined range. When the output of the fuel sender 255 goes out of the predetermined range, the detection is stopped even during the abnormality detection. Further, the predetermined range mentioned above, based on the output of the fuel sender 255 at abnormality detection start + side and with respect to the reference value Fu _B -
Have the same width ω on the sides.

As another example of the above-described method of setting the predetermined range, the fuel sender 2 during the calculation of ΔP1 or ΔP2 is used.
The smoothed value of the 55 output can be used as the reference value. However, in this case, the abnormality detection determination is ΔP1 or ΔP2.
Only during calculation.

Next, a flowchart of the fourth embodiment will be described with reference to FIG. In S101, the fuel amount Fu in the fuel tank 22 is read from the output of the fuel sender 255, and then the process proceeds to S102, where the fuel amount Fu is set to the reference value F.
compares the range of u _B ± omega, determines whether the state capable of anomaly detection.

If the determination is "YES", the flow advances to S120 to continue the process as in the above-described embodiment. If “NO” is determined, the process ends. In the above-described flow, the output of the fuel sender 255 is determined from the start to the end of the abnormality detection. However, when the determination is performed only during the calculation of ΔP1 or ΔP2, the same process as in S101 is performed before reading the pressure. What is necessary is just to perform a process.

FIG. 17 shows the structure of the canister according to the fifth embodiment of the present invention, which is used in place of the canister 30 and the canister closing valve 37 in FIG. In FIG. 17, a first check valve 302 is provided between an inlet port 15 of the canister 30 and an inlet pipe 301 connecting the adsorbent 34.
The first check valve 302 is provided so that the pressure in the fuel tank is higher than the atmospheric pressure by a predetermined value, for example, 15 mmHg.
It is opened when it becomes higher than the above, and is for introducing the fuel gas in the fuel tank into the canister 30. Further, between the introduction port 15 of the canister 30 and the hose connection portion 32a forming the outlet port, second and third check valves 303 and 304 in opposite directions are arranged in parallel. A canister closing valve 37 is arranged between the connection part 32a and the suction port 37a in the canister 30.

According to the embodiment shown in FIG. 17, during normal running of the vehicle, the canister closing valve 37 is opened, so that a larger intake pipe negative pressure (100 mmHg) than that of the internal combustion engine is obtained.
Above) is the canister closing valve 37 and the hose connection portion 32a.
, The second check valve 303 is closed. When the fuel temperature is increased, fuel gas is generated in the fuel tank, and when the pressure exceeds the opening pressure of the first check valve 302, the first check valve 302 is opened and the fuel gas in the fuel tank is adsorbed on the canister 30 by the adsorbent. 34. Here, the third check valve 304 opens when the pressure in the fuel tank becomes lower than the atmospheric pressure by a predetermined value (for example, 12 mmHg) or more, and guides the atmosphere into the fuel tank from the atmosphere port 36 through the kinister 30. This is for preventing deformation of the fuel tank.

When the canister closing valve 37 is closed to detect an abnormality in the evaporative purge system, the second check valve 303 supplies a large intake pipe negative pressure (10
0mmHg or more), the second check valve 3
0 indicates an open state, and the intake pipe negative pressure is supplied to the fuel tank via the second check valve 303. At this time, since the fuel tank side has a negative pressure, the first check valve 302 is closed, whereby the adsorbent 34 of the canister 30 can be bypassed to seal the evaporative purge system.

FIG. 18 shows the structure of the canister according to the sixth embodiment of the present invention, which is used in place of the canister 30 and the canister closing valve 37 in FIG. In FIG. 18, the canister 30 is divided into two rooms by partition walls 30b and 30c, and the adsorbents 34A and 34B are stored in each room, respectively, and have substantially two canister portions. . The filter 15 is disposed on the upper surface of the adsorbent 34B facing the air port 36. In addition, each partition 3
The rooms defined by 0b and 30c are connected via a switching valve 32.

[0083]

As described above in detail, according to the abnormality detecting device for a fuel evaporation control device of the present invention, it is possible to accurately detect an abnormality in the entire fuel evaporation control device from the fuel tank to the intake pipe.

In particular, according to the abnormality detecting device for a fuel evaporation control device according to the second aspect, when there is an abnormality which causes a leak such as breakage somewhere in the whole fuel evaporation prevention device from the fuel tank to the intake pipe. Can surely detect this.

Further, according to the third aspect of the present invention, when there is a blockage abnormality such as a collapse of a hose somewhere in the entire fuel evaporation prevention device from the fuel tank to the intake pipe, this is also reliably detected. be able to.

In addition, according to the device of the fourth aspect, a sensor having high pressure detection sensitivity can be used, and the abnormality detection accuracy can be improved. According to the fifth aspect of the present invention, in realizing each of the first to fourth aspects of the present invention, there is no possibility that an error occurs during use of the pressure sensor, and a highly reliable abnormality detection is always performed. be able to.

[Brief description of the drawings]

FIG. 1 is a basic configuration diagram illustrating a basic configuration of the present invention.

FIG. 2 is a schematic configuration diagram of an abnormality detection device for a fuel evaporation prevention device according to an embodiment.

FIG. 3 is a sectional view showing a schematic configuration of a canister closing valve.

FIG. 4 is a sectional view showing a schematic configuration of a purge control valve.

FIG. 5 is a graph showing characteristics of duty control in a purge control valve.

FIG. 6 is a flowchart of an abnormality detection process.

FIG. 7 is a flowchart of an abnormality detection process.

FIG. 8 is a timing chart illustrating a state during execution of the abnormality detection process.

FIG. 9 is a cross-sectional view illustrating a schematic configuration of a pressure sensor employed in a second embodiment.

FIG. 10 is a graph showing the relationship between the output voltage of a Hall element used in the pressure sensor of the second embodiment and the amount of magnet displacement.

FIG. 11 is a circuit configuration diagram in a hybrid IC in a pressure sensor according to a second embodiment.

FIG. 12 is a cross-sectional view illustrating the mounting relationship of the pressure sensor according to the second embodiment.

FIG. 13 is a cross-sectional view illustrating another mounting relationship of the pressure sensor according to the second embodiment.

FIG. 14 is a graph showing characteristics of a space volume of a fuel tank and a change in tank internal pressure in the third embodiment.

FIG. 15 is a flowchart of a main part of an abnormality detection process according to the third embodiment.

FIG. 16 is a flowchart of an abnormality detection process in the fourth embodiment.

FIG. 17 is a view showing a structure of a canister portion in a fifth embodiment.

FIG. 18 is a view showing a structure of a canister portion in a sixth embodiment.

[Explanation of symbols]

 Reference Signs List 2 intake pipe 6 accelerator pedal 8 throttle valve 22 fuel tank 22a relief valve 28 communication pipe 30 canister 34 adsorbent 36 atmosphere hole 37 canister closing valve 38 supply pipe 40 purge control valve 42 supply pipe 44 pressure sensor 50 electronic control circuit 62 throttle sensor 64 Idle switch 66 Vehicle speed sensor 100 Pressure sensor 109 Diaphragm 115,117 Pressure receiving plate 123 Rare earth magnet 125 Hall element 127 Hybrid IC

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F02M 25/08 F02M 25/08 301 F02B 77/08 G01M 15/00

Claims (9)

(57) [Claims] A fuel gas generated in a fuel tank is adsorbed as needed by an adsorbent of a canister provided in a purge passage communicating the fuel tank with an intake pipe, and purge control is performed according to an operation state of the internal combustion engine. A valve for opening and closing the valve to appropriately introduce the adsorbed fuel gas into the intake pipe to prevent evaporation of fuel; a pressure detecting means for detecting a pressure state in the fuel evaporation prevention device; An abnormality detection device for a fuel evaporation prevention device, comprising: an abnormality detection unit that detects an abnormality of the fuel evaporation prevention device based on a detection result of the pressure detection unit; and an air hole closing unit that closes an air hole provided in the canister. Closing means for closing the purge control valve and the air hole closing means together to make the whole fuel evaporation prevention apparatus one closed section; and adjusting the pressure in the closed section to a predetermined pressure. Closed section pressure adjusting means, and a pressure change state measuring means for measuring a predetermined pressure change state at the time of pressure adjustment by the closed section pressure adjusting means or after the pressure adjustment; An abnormality detection device for a fuel evaporation prevention device, wherein an abnormality of the fuel evaporation prevention device is detected from a change state. 2. The abnormality detection device for a fuel vaporization prevention device according to claim 1, wherein the closed section pressure adjusting means switches and adjusts the pressure in the closed section to a first predetermined pressure and a second predetermined pressure. The pressure change state measuring means measures a first pressure change state after being adjusted to the first predetermined pressure and a second pressure change state after being adjusted to a second predetermined pressure. An abnormality detection device for a fuel evaporation prevention device, wherein the abnormality detection means detects an abnormality of the fuel evaporation prevention device by comparing the first and second pressure change states. 3. The abnormality detection device for a fuel vaporization prevention device according to claim 1, wherein the closed section pressure adjusting means introduces a negative pressure from near an intake pipe side end, and wherein the pressure change state measuring means includes: Measuring a pressure change state at the time of introducing a negative pressure, wherein the abnormality detecting means detects an abnormality of the fuel evaporation prevention device based on the pressure change state at the time of the introduction of the negative pressure; Device abnormality detection device. 4. An abnormality detection device for a fuel evaporation prevention device according to claim 1, wherein said pressure detection means is disposed in a section from said fuel tank to a canister. Abnormality detection device for fuel evaporation prevention device. 5. The abnormality detection device for a fuel vaporization prevention device according to claim 1, wherein the pressure detection unit is attached to the displacement member that is displaced in accordance with a pressure. An abnormality detection device for a fuel evaporation prevention device, comprising: a magnetic member; and a Hall element for changing an output based on a displacement of the magnetic member. 6. An abnormality detecting device for a fuel evaporation control device according to claim 1, wherein said fuel amount detecting means detects a fuel amount of said fuel tank, and said fuel amount detected by said fuel amount detecting means. An abnormality determination criterion varying means for changing a criterion for detecting an abnormality of the abnormality detection means in accordance with an amount of the abnormality detection means. 7. An abnormality detection device for a fuel evaporation prevention device according to claim 1, wherein said fuel amount detection means detects a fuel amount of said fuel tank, and said fuel amount detected by said fuel amount detection means. A fuel fluctuation detecting means for judging whether or not the fuel amount fluctuates, and when the fuel amount fluctuates, a fuel fluctuation detecting means for substantially disabling abnormality detection in the abnormality detecting means. Abnormality detection device for prevention device. 8. The abnormality detection device for a fuel vaporization prevention device according to claim 1, wherein the canister has substantially two canister portions, and the two canister portions are the air holes. They are connected via closing means. 9. The abnormality detection device for a fuel vaporization prevention device according to claim 1, wherein the air hole closing means is disposed in the canister, and further, when the air hole closing means is closed. An abnormality detection device for a fuel evaporation prevention device, comprising: a check valve means for bypassing the adsorbent to communicate between an introduction port and an exit port of the canister.